The present invention relates generally to respiratory devices, and more particularly to humidifier devices delivering to a patient gases that have a controlled vapor level and temperature.
When a healthy person breathes atmospheric air, the air passages of the person supply heated moisture to the inhaled gases, and the person's body generates the required amount of heat and moisture to satisfy the individual's respiratory needs. However, for patients that fail to satisfy their respiratory needs by breathing from the ambient environment (e.g., unhealthy children needing a higher concentration of water vapor in their breathable air), it becomes necessary to supply additional water to a humidifier chamber of an optionally heated humidifier device to achieve an elevated moisture concentration level in the patient's breathable air.
Known systems for providing heated and moisturized respiratory gases to patients basically fall into two groups: nebulizers, which produce aerosols of fine water droplets; and heated humidifiers, which supply heat and moisture to a gas by the passage of the gas through or over a heated water bath or evaporated surface. The present invention is directed to heated humidifiers.
One such humidifier system includes a rigid, refillable water container designed to be placed upon a base unit having a heating element and is disclosed in U.S. Pat. No. 5,195,515 to Levine, which is herein incorporated by reference. This system includes a disposable heated cartridge humidifier for use with a collapsible water supply container and a heating device. The cartridge housing has a base plate fabricated from a conductive material such as metal, preferably aluminum.
Another known humidifier system having a gravity feed collapsible water supply bag is disclosed in U.S. Pat. No. 5,943,473 also to Levine, which is herein incorporated by reference. This system includes a humidifier cartridge for engaging a heating unit. The humidifier cartridge has a water inlet adapted to be connected to the gravity feed bag and is in fluid communication with a chamber of the humidifier cartridge.
One problem with known humidifiers using gravity feed collapsible water supply bags is that these water supply bags cannot supply water to the humidifier chamber during the feeding of water to the humidifier chamber, when increased air pressure within the humidifier chamber exceeds the air pressure in the water supply bags. This higher air pressure in the humidifier chamber inhibits water flow from the water supply bag to the humidifier chamber, resulting in humidifier devices that deliver to patients insufficient breathable gas supplies having controlled vapor levels and temperatures.